Mendel and Darwin's Problem

Reading Assignment

Read about Gregor Mendel (Brother Gregory) and Charles Darwin. Find out who Darwin was, where he lived, what was he famous for, and what kind of contribution did he make to science. Once again, begin by reading the fictionalized story and discover the main characters. Later re-read this material and follow the hyperlinks in the text that lead to the various scientific principles concerning Darwin, his work and the work of others.

2) The e-textbook: Darwin and Natural Selection and Evolution in Action.
This material explains what Darwin found, how natural selection works, variation, and agents of change.

The e-textbook and the material on the WWW complement each other. Pay particular attention to the subject of variation.

First "Assignment Questions":

1. Who was Charles Darwin? Where and when did he live? What was his personal background?
   (write at least two or three paragraphs).

2. What events in Darwin's life influenced him the most, and why? What role did his friends play in the story of these discoveries?

3. What was the major principle(s) discovered by Darwin? Give your reasons.

4. How were Darwin's discoveries greeted by other scientists? Contrast this with the way he work was greeted by non-scientists.

5. Why would Brother Gregory's work on genetics have helped Darwin? What did Mendel know that Darwin didn't?

   (You should create a word processor document of your answers to the assigned questions. Then (a) post the resulting document on the appropriate page of the newsgroup (if required), and (b) keep it safe for possible inclusion in your portfolio.)

2) Here is your second research assignment from Brother Gregory.

As he walked along the floor he noticed that each slab of rock represented a slice of time, one older than the next. The tile nearest to the door was cut from the youngest part of the rock, and each subsequent tile had been cut from older an older layers. He was looking at samples of organisms that lived millions of years ago, and as the tiles (or slices through the rock) got older and older, the fossilized organisms seemed to change in various ways; some got bigger, some changed shape, some vanished and new ones appeared. It suddenly occurred to him that there were patterns in the way these creatures evolved through time!

Brother Gregory took careful measurements from these "slices through time". He made drawings of the creatures he found in each slice. All of them had bodies that could be divided up into three parts, so he called them "Three-part-ites" or "Three - part - creatures". He measured their sizes, counted their numbers and then made a careful diagram of each tile showing the distribution and location of each type of "Threepartite" across the surface.

He also made one other kind of measurement. The same tiles were used to make steps, so he could measure the thickness of each layer of rock. This thickness could then be used to work out how old that 'slice' was. All he needed was the rate at which the rock formed. A book on geology gave him the answer. This type of rock was formed as sand and other sediment fell to the bottom of the sea and became compacted (pressed down) by more and more material falling on it from above.

Knowing how old the youngest layer was, and knowing the rate (how fast) the sediment formed, it should be possible to work out how long ago each layer of fossil containing rock was laid down. The animals trapped in the rock at the time of their death should be as old as the rock in which they were fossilized. Mendel was good at numbers, so a simple calculation gave him the answer.

Brother Gregory wants you, his researcher, to examine this data (choose any two of the five sets of tiles given below), the thickness of the rock, the rates of sedimentation, and make diagrams of the patterns of evolution of all the creatures found in all these sets of tiles. These patterns are called "phylogenies" (family trees), and show the macroevolution of these creatures over long periods of time.

All the information Mendel collected are organized into the following five sets of data.

You should put into their portfolio:

1. A list of binomial names (scientific "two word" names) for all the "Threepartites" seen. You can make up your own names, but, you must (i) follow approved naming conventions, and (ii) the genus names must conform to the patterns of evolution you find (you cannot simply rename each creature arbitrarily). How many species do you think you see in these tiles/sequences?
2. A phylogeny (family tree) for the creatures seen in each set of tiles (Sets A through E). These phylogenies should represent the pattern(s) of evolution seen in that sequence. These diagrams can take any one of several different forms, so you should find out first what type of diagrams you intend to make before you start working with your data.
3. There are different patterns to be found in each set of tiles. Once you have the pattern, describe what has happened to the "Threepartites" and what principles of evolution the pattern represents.

Second "Assignment Questions":

1. What is a phylogeny? Your answer should include an explanation of anagenesis and cladogenesis.

2. Give two examples of trends or patterns seen in various phylogenies. What type of events are being see?.

3. Why do scientists study phylogenies? What can we learn from them?

4. Other than the examples in this exercise, give two other examples of well studied phylogenies.

5. What role does adaptation and variation play in determining the patterns of evolution?

   (You should create a word processor document of your answers to the assigned questions. Then (a) post the resulting document on the appropriate page of the newsgroup (if required), and (b) keep it safe for possible inclusion in your portfolio.)